Nanotechnology holds great promise for the development of effective diagnostic and therapeutic methods for diseases such as cancer, atherosclerosis, and stroke. In the pursuit of nanotechnology-based therapies, much effort is devoted to the generation and use of biocompatible nanoparticles tailored to have specific physical properties such as high absorptivity for specific wavelengths. For example, “nanoshells” were developed as optically tunable nanoparticles composed of a silica core coated with an ultrathin metallic layer (e.g., gold). The high intrinsic optical absorptivity of nanoshells has been exploited, e.g., to heat-ablate tumors by near-infrared irradiation of nanoshells in vivo.